Method for producing imprint mold and magnetic recording medium

ABSTRACT

According to one embodiment, a method for producing an imprint mold includes forming, on a substrate, a plurality of guides including a first wall surface and a second wall surface, wherein an angle between at least one of the first and second wall surfaces and an exposed substrate surface is 131° or less, applying a self-assembling material, which forms a sphere when phase-separated, to a guide groove area defined by the first wall surface, the second wall surface and the substrate surface, and self-assembling the self-assembling material to form a dot pattern, etching the substrate by using the dot pattern as a mask to transfer the dot pattern and forming an imprint mold by using the substrate with the dot pattern transferred as a master mold.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2010-102573, filed Apr. 27, 2010; theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a method for producingan imprint mold and a method for producing a magnetic recording medium.

BACKGROUND

With a view to achieving a higher capacity of a magnetic recordingapparatus like a hard disk, the increase in recording density of amagnetic recording medium included in such a magnetic recordingapparatus has been intended. Bit patterned media (BPM) is a type ofmagnetic recording medium developed for such a purpose. In the BPM, asingle magnetic dot functions as a single recording unit. When thismagnetic dot exists while shifting from an assumed position, an exactaccess of a read/write head to the magnetic dot is hindered, whichconsequently leads to an error of writing and reading. Accordingly, interms of the BPM performance, it is important that these magnetic dotsare exactly arrayed.

BRIEF DESCRIPTION OF THE DRAWINGS

A general architecture that implements the various features of theembodiments will now be described with reference to the drawings. Thedrawings and the associated descriptions are provided to illustrate theembodiments and not to limit the scope of the invention.

FIGS. 1A, 1B, 1C, 1D, 1E and 1F are cross-sectional views each showing amethod for producing a first guide stamper according to a firstembodiment;

FIGS. 2A, 2B, 2C, 2D, 2E, 2F, 2G and 2H are cross-sectional views eachshowing a method for producing an imprint mold and a magnetic recordingmedium according to the first embodiment;

FIGS. 3A, 3B, 3C and 3D are cross-sectional views each showing apositional relation between a guide and a sphere in the embodiment;

FIGS. 4A, 4B and 4C are cross-sectional views each showing a relationbetween an angle of a wall surface of the guide and a state of thesphere to be formed;

FIGS. 5A, 5B, 5C, 5D, 5E, 5F and 5G are cross-sectional views eachshowing a method for producing a second guide stamper according to asecond embodiment;

FIGS. 6A, 6B, 6C, 6D, 6E, 6F, 6G and 6H are cross-sectional views eachshowing a method for producing an imprint mold and a magnetic recordingmedium according to the second embodiment; and

FIG. 7 is a graph showing a relation between an angle of a wall surfaceof the guide and a state of the sphere to be formed.

DETAILED DESCRIPTION

Various embodiments will be described hereinafter with reference to theaccompanying drawings.

In general, according to one embodiment, there is provided a method forproducing an imprint mold, comprising forming, on a substrate, aplurality of guides comprising a first wall surface and a second wallsurface, wherein an angle between at least one of the first and secondwall surfaces and an exposed substrate surface is 131° or less, applyinga self-assembling material, which forms a sphere when phase-separated,to a guide groove area defined by the first wall surface, the secondwall surface and the substrate surface, and self-assembling theself-assembling material to form a dot pattern, etching the substrate byusing the dot pattern as a mask to transfer the dot pattern and formingan imprint mold by using the substrate with the dot pattern transferredas a master mold.

<Method for Producing Imprint Mold>

A method for producing an imprint mold according to a first embodimentwill be described below.

First, based on FIGS. 1A to 1F, a method for producing a first guidestamper 15 used in the method for producing the imprint mold accordingto the first embodiment will be described.

As shown in FIG. 1A, a sputter carbon layer 13 and a silicon mask 12 aresputtered on a silicon substrate 14 in this order to thereafter apply anelectron beam resist 11.

As shown in FIG. 1B, part of the electron beam resist 11 is removed byelectron beam drawing and development to form a pattern of protrusionsand recesses. This pattern comprises an area corresponding to a guideand an area corresponding to a groove between the guides.

As shown in FIG. 1C, the silicon mask 12 is etched by using the electronbeam resist 11 with the pattern of protrusions and recesses formed as amask to expose the sputter carbon layer 13 in the area of recesses. Atthis time, CF₄ is used as an etching gas.

As shown in FIG. 1D, the sputter carbon layer 13 is etched by using thesilicon mask 12 with the pattern of protrusions and recesses formed as amask. Ar is used as an ion milling gas. At this time, the recess of thesputter carbon layer 13 is etched while tapered. That is to say, therecess is formed so as to narrow downward. In FIG. 1D, an angle betweena wall surface of the sputter carbon layer 13 and an exposed surface ofthe silicon substrate 14 is an obtuse angle. In the first embodiment,this angle is approximately the same on either side of the recess of thesputter carbon layer 13.

As shown in FIG. 1E, the silicon mask 12 remaining on the protrusion ofthe sputter carbon layer 13 is removed by etching with the use of CF₄gas.

As shown in FIG. 1F, electroforming in which the pattern of protrusionsand recesses of the sputter carbon layer 13 is used as a mold isperformed to form the first guide stamper 15. This first guide stamper15 has the pattern of protrusions and recesses corresponding to those ofthe sputter carbon layer 13 used as the mold. Accordingly, a taper of aprotrusion of the first guide stamper 15 is at approximately the sameangle on either side.

As described above, the first guide stamper 15 according to the firstembodiment is formed.

Next, based on FIGS. 2A to 2H, the method for producing an imprint mold23 according to the first embodiment, in which the first guide stamper15 is utilized, will be described.

As shown in FIG. 2A, an imprint resist 21 is applied on a siliconsubstrate 22. Next, the pattern of protrusions and recesses of the firstguide stamper 15 produced as described above is imprinted on the imprintresist 21. That is to say, a face having the pattern of protrusions andrecesses of the first guide stamper 15 is pressed against a surface ofthe imprint resist 21.

As shown in FIG. 2B, the pressed first guide stamper 15 is removed. Atthis time, though not shown in FIG. 2B, a residual layer of the imprintresist 21 remains on a bottom face of a recess formed in the imprintresist 21. This residual layer is removed by etching to expose a surfaceof the silicon substrate 22 in the recess, so that the imprint resist 21is segmented to form a guide 21 a. This guide 21 a has a shapecorresponding to the first guide stamper 15. That is to say, an angle θbetween a wall surface of the guide 21 a and an exposed surface of thesilicon substrate is an obtuse angle. Specifically, θ is 131° or less,preferably θ is 120° or more and 131° or less.

Here, in considering the single guide 21 a, this guide 21 a includes theother wall surface (a second wall surface) on the opposite side of onewall surface (a first wall surface). In considering the two guides 21 aarranged side by side, a wall surface (a first wall surface) of oneguide 21 a is opposite to a wall surface (a second wall surface) of theother guide 21 a. Thus, it is understood that an expression “the guide21 a includes the first wall surface and the second wall surface”includes both the case of assuming the single guide 21 a and the case ofassuming the two guides 21 a arranged side by side. As shown in FIG. 2B,in the producing method according to the first embodiment, an anglebetween the exposed surface of the silicon substrate 22 and the firstwall surface of the guide 21 a is approximately the same as an anglebetween the exposed surface of the silicon substrate 22 and the secondwall surface of the guide 21 a.

A grooved area defined by the wall surfaces of the two guides 21 aarranged side by side and the exposed surface of the silicon substrate22 may be expressed as “a guide groove area”.

As shown in FIG. 2C, a self-assembling material is applied in the guidegroove area and phase-separated into a sphere 27 and a matrix 28 bysubsequently inducing self organization. These processes are performed,for example, in such a manner that polystyrene-polydimethylsiloxanediblock copolymer (PS-PDMS) (molecular weight of PS: 11700, molecularweight of PDMS: 2900) solution is applied in the guide groove area byspin coating and then phase-separated into PDMS (the sphere 27) and PS(the matrix 28) by annealing at a temperature of 180° C. A material toform a sphere (a globe) by phase-separation other than PS-PDMS may alsobe used as the self-assembling material. In these processes, the sphere27 is formed in a regular array while separated at even intervals,preferably into a layer.

As shown in FIGS. 2D and 2E, the silicon substrate 22 is etched by usingthe sphere 27 formed by phase separation as a mask. At this time, forexample, CF₄ is used as an etching gas. The spheres 27 are arrayed whilehaving a regular dot pattern at even intervals, so that siliconsubstrate dots 22 a arrayed with a regular dot pattern at even intervalsmay be formed on the silicon substrate 22 by etching with the use of thesphere 27 as a mask.

As shown in FIG. 2F, the imprint mold 23 is formed by electroforming inwhich the silicon substrate 22 with the dot pattern formed is used as amold. Thus, an exact dot pattern comprising a multitude of dottedrecesses is formed in the imprint mold 23.

As described above, the imprint mold 23 according to the firstembodiment is formed.

The angle of the taper of the protrusion of the first guide stamper 15as shown in FIG. 2A does not exactly need to correspond to the angle θof the guide 21 a. The angle θ may be formed in the guide 21 a at astage of finishing a process as shown in FIG. 2B. Accordingly, iffinally capable of achieving the angle θ of the guide 21 a, the angle ofthe taper of the protrusion of the first guide stamper 15 and the anglebetween the wall surface of the recess of the sputter carbon layer 13and the surface of the silicon substrate 14 as shown in FIG. 1D are notlimited.

A process of forming the guide 21 a on the silicon substrate 22 as shownin FIG. 2B is not limited to the case of utilizing the first guidestamper 15. For example, after forming an approximately rectangularrecess in the imprint resist 21, the angle of θ may be achieved byengraving the wall surface with milling. In addition, a techniquecapable of forming the angle θ may be utilized.

<Method for Producing Magnetic Recording Medium>

Based on FIGS. 2G and 2H, a method for producing a magnetic recordingmedium according to the embodiment, in which the imprint mold 23 isutilized, will be described below.

First, as shown in FIG. 2G, a magnetic recording layer 25 is formed on aglass substrate 26 to apply an imprint resist 24 thereon.

Next, the dot pattern of the imprint mold 23 produced as described aboveis imprinted on this laminate. The dot pattern is formed on the imprintresist 24 by pressing a face having the dot pattern of the imprint mold23 against the imprint resist 24 of the laminate.

As shown in FIG. 2H, the magnetic recording layer 25 is subjected tomilling processing by using the imprint resist with the dot patternformed as a milling mask. Thus, a magnetic dot comprising an exactlydesired pattern is formed on the glass substrate 26.

Thereafter, the magnetic recording medium having the regular magneticdot pattern may be produced by properly performing embedding of anon-magnetic substance and formation of a protective film.

<Regarding Angle of Wall Surface of Guide>

A relation between the angle of the guide wall surface and the dotpattern formed by the self-assembling material will be described below.

FIGS. 3A and 3B are cross-sectional views showing the two guides 21 aarranged side by side and the sphere 27 formed therebetween in theproducing method according to the embodiment. In these FIGS. 3A and 3B,in order to show a positional relation between the sphere and theguides, the matrix 28 in FIGS. 2C and 2D is omitted.

As shown in FIGS. 3A to 3D, in the producing method according to theembodiment, the angle θ between the wall surface of the guides 21 a andthe surface of the silicon substrate 22 is 131° or less, preferably 120°or more and 131° or less. FIG. 3A shows the case where a width of theguide groove between the two guides 21 a arranged side by side is themost appropriate for an array of the sphere 27. As shown in FIG. 3B,even in the case where the width of the guide groove becomes narrowerthan an optimum value, the sphere 27 is stably formed in a state ofrunning on the inclined wall surface of the guides 21 a. Thus, the wholearray of the sphere 27 is also made into an assumed pattern. The use ofthe guides 21 a according to the embodiment allows the imprint mold 23and the magnetic recording medium, in which the assumed dot pattern isexactly reproduced, to be produced even in the case where a size and ashape of the guides 21 a are disordered. FIGS. 3A and 3B signify thecase where the width of the guide groove is wide and narrowrespectively, based on L₁>L₂ with regard to an edge distance of each ofthe guides 21 a.

FIGS. 3C and 3D show the case where the tilt angle θ of the guides isless than 120°. In the case of L₁>L₂ with regard to the edge distance ofthe guides 21 a, a pitch between the spheres 27 narrows, or as shown inFIG. 3D, the number of the spheres arrayed in the guides becomes lessthan the case of being arrayed at the proper pitch therebetween, and thedesired pattern is not obtained resulting in a defect.

Next, based on FIGS. 4A to 4C, the angle θ between the wall surface ofthe guides 21 a and the surface of the silicon substrate 22 will bedescribed. In these FIGS. 4A to 4C, in order to show a positionalrelation between the sphere and the guides, the matrix 28 in FIGS. 2Cand 2D is omitted.

In the embodiment, this angle θ is 131° or less. This condition, asshown in FIG. 4B, may restrain the sphere 27 from being formed on theguide 21 a. FIG. 4A shows the case where 9 is more than 131° and asphere 27 a is formed on the guide 21 a. The reason therefor is that 9is so large that the sphere 27 a is at the same position as asecond-layer sphere 27 b of a self-assembling pattern virtually shown inFIG. 4A and no energy loss is caused even though the sphere is formedfrom the guide groove onto the guide 21 a. In other words, this isbecause, in the case where an inclination of the guide 21 a is small (θis large), the sphere 27 a is stably formed on the inclination.

The fact that the angle at a boundary between the case where the sphere27 a is formed on the guide 21 a and the case where it is not formed is131° may be derived as follows.

The energy of the two spheres 27 formed along the wall surface of theguide 21 a is most stable in the case where these are in a relation of ahexagonal lattice. That is to say, in the case where the angle θ of thewall surface of the guide 21 a is an angle capable of forming such ahexagonal lattice, the sphere 27 a is stably formed on the guide 21 a.On the other hand, a smaller angle than this angle prevents stableformation of the hexagonal lattice. That is to say, the angle θ as theboundary is an angle capable of forming the hexagonal lattice.

In FIG. 4A, when the layer of the sphere 27 formed directly on thesilicon substrate 22 is considered as a first layer, the sphere 27 a onthe guide 21 a is formed as a second layer. The angle θ of the wallsurface of the guide 21 a is reflected in a positional relation betweenthe sphere 27 of the first layer and the sphere 27 a of the secondlayer, so that the angle θ capable of forming the hexagonal lattice isobtained by considering the relation between the sphere 27 of the firstlayer and the sphere 27 a of the second layer in the hexagonal lattice.That is to say, an expression of tan(180°−θ)=2/√3 may be introduced andθ is an angle slightly larger than 131°. Accordingly, the case where θis 131° or less may restrain the sphere 27 from being formed on theguide 21 a.

In addition, in the embodiment, the angle θ is preferably 120° or more.This condition, as shown in FIG. 4B, allows the pitch between thespheres 27 to be even. FIG. 4C shows the case where θ is less than 120°,and the matrix component in a portion shown by a reference numeral 28 aeasily becomes sparse in a guide corner section of the sphere 27 closestto the guide 21 a. Thus, a distortion occurs in the array of the sphere27 in the vicinity of the guide. This distortion causes unevenness ofthe pitch. On the other hand, the case where the angle of the corner is120° minimizes the occurrence of the distortion of the sphere 27.Accordingly, the case where θ is 120° or more allows the pitch betweenthe spheres 27 to be even.

In the specification, the dot pitch between the spheres 27, between thesilicon substrate dots 22 a and between the magnetic dots 25 a signifiesa distance between centers of the spheres or the dots in any case.

The angle θ between the wall surface of the guides 21 a and the surfaceof the silicon substrate 22 may be measured by a known method; forexample, the angle θ may be measured by observing a cross section withthe use of a scanning electron microscope (SEM).

MODIFICATION EXAMPLE

The method for producing the imprint mold and the method for producingthe magnetic recording medium according to the embodiment are notlimited to the first embodiment and may assume a second embodimentdescribed below.

FIGS. 5A to 5G show a method for producing a second guide stamper 16used in a method for producing an imprint mold 23 according to thesecond embodiment.

The processes in FIGS. 5A to 5D are the same as those shown in FIGS. 1Ato 1D, respectively, in the method for producing the first guide stamper15.

As shown in FIG. 5E, one of wall surfaces of a recess formed in asputter carbon layer 13 is processed and formed into a rectangle, forexample. This processing, for example, is performed by inclining alaminate to etch the wall surface to be processed. Thus, a pattern ofprotrusions and recesses, in which angles of the opposite wall surfacesin the recess of the sputter carbon layer 13 are different, is formed.

FIGS. 5F and 5G are the same as the processes shown in FIGS. 1E and 1F,respectively, in the method for producing the first guide stamper 15.

The second guide stamper 16, in which the angles of the right and leftwall surfaces of the recess are different from each other, is formed bythe producing method of the embodiment shown in FIGS. 5A to 5G, as shownin FIG. 5G.

FIGS. 6A to 6H show the method for producing the imprint mold 23 and themethod for producing the magnetic recording medium according to thesecond embodiment, formed by using the second guide stamper 16.

The processes in FIGS. 6A to 6H are the same as FIGS. 2A to 2H,respectively, in the producing method according to the first embodiment.

However, as shown in FIG. 6B, an angle θ₁ between a first wall surfaceand an exposed surface of a silicon substrate 22 is different from anangle θ₂ between a second wall surface and the exposed surface of thesilicon substrate 22; in FIG. 6B, θ₂ is 120° or more and 131° or lesswhile θ₁ is an angle approximate to a right angle. Thus, if one anglesatisfies the condition of being 131° or less, preferably 120° or moreand 131° or less, even though the other angle does not satisfy thecondition, an exact dot pattern may be formed in the same manner as theimprint mold 23 or the magnetic recording medium according to the firstembodiment.

Example 1

A first guide stamper 15 for producing a guide was produced by a methodshown in FIGS. 1A to 1F.

As shown in FIG. 1A, a 40-nm sputter carbon layer and a 5-nm siliconsputter film were formed on a silicon substrate 14. An electron beamresist 11 (ZEP manufactured by ZEON CORPORATION) was applied thereon.

As shown in FIG. 1B, electron beam drawing and development wereperformed for the electron beam resist 11 to form a desired guidepattern.

As shown in FIG. 1C, the silicon hard mask 12 was etched by using theelectron beam resist 11 with the pattern formed as a mask with the useof CF₄ gas. Thus, the pattern was transferred to the silicon hard mask12.

As shown in FIG. 1D, the sputter carbon layer 13 was processed by Ar ionmilling with the use of the silicon hard mask 12 with the pattern formedas a mask. Thus, a groove having a taper at an angle of 120° wasproduced.

As shown in FIG. 1E, the silicon mask 12 remaining on the sputter carbonlayer 13 was removed by etching with the use of CF₄ gas.

As shown in FIG. 1F, the first guide stamper 15 in which edges on bothsides of a protrusion were 120° was produced by nickel electroformingwith the use of the guide pattern formed in the sputter carbon layer 13as a mold.

Modification Example 1

A second guide stamper 16 for producing a guide was produced by a methodshown in FIGS. 5A to 5G.

The processes in FIGS. 5A to 5D were performed in the same manner as theprocesses in FIGS. 1A to 1D of Example 1 to form a groove, in whichangles of both tapers were 120°, in a sputter carbon layer 13.

As shown in FIG. 5E, the angle of one taper was made into 105° byetching while inclining a substrate angle.

As shown in FIG. 5F, a silicon mask 12 remaining on the sputter carbonlayer 13 was removed by etching with the use of CF₄ gas.

As shown in FIG. 5G, the second guide stamper 16 in which an edge on oneside of a protrusion was 120° and an edge on the other side was 105° wasproduced by nickel electroforming with the use of a guide pattern formedin the sputter carbon layer 13 as a mold.

Example 2

A self-assembling pattern was formed by a method shown in FIGS. 2A to 2Don a silicon substrate 22 with a guide 21 a formed.

As shown in FIG. 2A, an imprint resist 21 was applied on the siliconsubstrate 22.

As shown in FIG. 2B, a first guide stamper 15 produced in Example 1 waspressed against the imprint resist 21 to transfer a pattern ofprotrusions and recesses. When a width of a bottom of a formed recesswas measured at a plurality of points, dispersion was observed in therange of 85 nm to 93 nm.

As shown in FIGS. 2C and 2D, a polystyrene-polydimethylsiloxane diblockcopolymer (PS-PDMS, molecular weight of PS: 11700, molecular weight ofPDMS: 2900) solution was applied in a produced groove between the guidesby spin coating to induce phase separation by subsequently annealing ata temperature of 180° C. and form a sphere 27. When a pitch of theformed sphere 27 was measured at a plurality of sphere intervals, eachof the sphere intervals was 17 nm.

Modification Example 2

A self-assembling pattern was formed by a method shown in FIGS. 6A to 6Don a silicon substrate 22 with a guide 21 a formed.

As shown in FIG. 6A, an imprint resist 21 was applied on the siliconsubstrate 22.

As shown in FIG. 6B, a second guide stamper 16 produced in ModificationExample 1 was pressed against the imprint resist 21 to transfer apattern of protrusions and recesses. When a width of a bottom of aformed recess was measured at a plurality of points, dispersion wasobserved in the range of 85 nm to 93 nm.

As shown in FIGS. 6C and 6D, a polystyrene-polydimethylsiloxane diblockcopolymer (PS-PDMS, molecular weight of PS: 11700, molecular weight ofPDMS: 2900) solution was applied in a produced groove between the guidesby spin coating to induce phase separation by subsequently annealing ata temperature of 180° C. and form a sphere 27. When a pitch of theformed sphere 27 was measured at a plurality of sphere intervals, eachof the sphere intervals was 17 nm.

Example 3

An imprint mold 23 and a magnetic recording medium were produced by amethod shown in FIGS. 2D and 2H.

As shown in FIGS. 2D and 2E, a silicon substrate 22 was etched by usinga self-assembling pattern produced in Example 2 as a mask with the useof CF₄ gas. Thus, a pattern in which silicon substrate dots 22 a werearrayed at a pitch of 17 nm was formed on a surface of the siliconsubstrate 22.

As shown in FIG. 2F, the imprint mold 23 was formed by nickelelectroforming with the use of the silicon substrate 22 with the patternformed as a mold.

As shown in FIG. 2G, a desired magnetic recording layer 25 was formed ona glass substrate 26 to further apply an imprint resist 24. The imprintmold 23 was pressed thereon to transfer a dot pattern of the imprintmold 23.

As shown in FIG. 2H, the magnetic recording layer 25 was subjected tomilling processing by using the imprint resist 24 with the dot patterntransferred as a milling mask, so that the dot pattern with magneticdots 25 a arrayed was produced on the glass substrate 26.

Example 4

The influence of an angle θ between a wall surface of a guide 21 a andan exposed surface of a silicon substrate 22 on a pitch between spheres27 and the formation of the spheres 27 on the guide 21 a was studied.

The silicon substrate 22 with the guide 21 a formed thereon, as shown inFIG. 2D, was produced. At this time, 12 kinds in total were produced,such that θ was 105°, 120°, 135° or 150°, and a guide width (a distanceof a bottom between the guides) was 85 nm, 88 nm or 93 nm. Aself-assembling material was applied to the produced substrate andannealed at a temperature of 180° C. to thereby form the spheres 27.

With regard to each substrate, a plurality of pitches between thespheres 27 were measured by using SEM. The results are shown in FIG. 7.In FIG. 7, the horizontal axis signifies the angle θ and the leftvertical axis signifies an average value (nm) of the pitches between thespheres 27, and plots common in the guide width are joined by a curve.In addition, with regard to the substrate having a guide width of 85 nm,an area of the spheres 27 formed on the guide 21 a was measured by usingSEM. The results are shown in FIG. 7. In FIG. 7, the horizontal axissignifies the angle θ and the right vertical axis signifies a ratio ofthe area in which the spheres 27 were formed on the guide 21 a. Theratio was calculated as an area of the spheres 27 to a projected area ofan inclined plane of the guide 21 a.

Regarding the pitches, three curves different in the guide widthseparated in the case where θ was small and converged as θ becamelarger. Specifically, when θ was 105°, the pitches offered values from17 nm to 19 nm according to a difference in the guide width. On theother hand, when θ was 120° or more, the pitches were approximately 17nm regardless of the difference in the guide width. It is understoodfrom this fact that a determination of θ at 120° or more allows thepitches between the spheres to be kept constant even though dispersionis caused in the guide width.

Regarding the area, the area of the spheres formed on the guide 21 aincreased as θ became larger. Specifically, the ratio was 10% or less at105° and 120°; on the contrary, the ratio increased abruptly when θexceeded 120°, and the ratio reached around 30% and 70% at 134° and150°, respectively. It is understood from this fact that a smaller valueof θ more restrains the spheres 27 from being formed on the guide 21 a.

Through a summary of the results with regard to the pitches and theresults with regard to the area, it is understood that when θ is in therange of 120° to 135°, even in the case where dispersion is caused inthe guide width, the pitches between the spheres may be kept constantand the formation of the spheres on the guide may be restrained at aconstant level to induce self organization.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

1. A method for producing an imprint mold, comprising: forming, on asubstrate, a plurality of guides comprising a first wall surface and asecond wall surface, wherein an angle between at least one of the firstand second wall surfaces and an exposed substrate surface is 131° orless; applying a self-assembling material, which forms a sphere whenphase-separated, to a guide groove area defined by the first wallsurface, the second wall surface and the substrate surface, andself-assembling the self-assembling material to form a dot pattern;etching the substrate by using the dot pattern as a mask to transfer thedot pattern; and forming an imprint mold by using the substrate with thedot pattern transferred as a master mold.
 2. The method of claim 1,wherein the angle is 120° or more and 131° or less.
 3. The method ofclaim 1, wherein the angle between the first wall surface and thesubstrate is approximately the same as the angle between the second wallsurface and the substrate.
 4. The method of claim 1, wherein one of theangle between the first wall surface and the substrate and the anglebetween the second wall surface and the substrate is 90° or more andless than 120°.
 5. The method of claim 1, wherein the self-assemblingmaterial is a polystyrene-polydimethylsiloxane diblock copolymer.
 6. Amethod for producing a magnetic recording medium, comprising: forming aresist on a magnetic recording layer; imprinting the resist with animprint mold produced by the method of claim 1 to transfer the dotpattern; removing a residue remaining in a recess of the patternedresist; and etching the magnetic recording layer by using the patternedresist as a mask to transfer the dot pattern.